Over the years, there has been developed a substantial body of patent and other literature directed to the formation and properties of poly(aryl ethers) (hereinafter called "PAE"). Some of the earliest work such as by Bonner, U.S. Pat. No. 3,065,205, involves the electrophilic aromatic substitution (viz. Friedel-Crafts catalyzed) reaction of aromatic diacylhalides with unsubstituted aromatic compounds such as diphenyl ether. The evolution of this class to a much broader range of PAEs was achieved by Johnson et al., Journal of Polymer Science, A-1, vol. 5, 1967, pp. 2415-2427, Johnson et al., U.S. Pat. Nos. 4,108,837, and 4,175,175. Johnson et al. show that a very broad range of PAES can be formed by the nucleophilic aromatic substitution (condensation) reaction of an activated aromatic dihalide and an aromatic diol. By this method, Johnson et al. created a host of new PAEs including a broad class of poly(aryl ether ketones), hereinafter called "PAEK".
In recent years, there has developed a growing interest in PAEKs as evidenced by Dahl, U.S. Pat. No. 3,953,400; Dahl et al., U.S. Pat. No. 3,956,240; Dahl, U.S. Pat. No. 4,247,682; Rose et al., U.S. Pat. No. 4,320,224; Maresca, U.S. Pat. No. 4,339,568; Attwood et al., Polymer, 1981, vol 22, August, pp. 1096-1103; Blundell et al., Polymer, 1983 vol. 24, August, pp. 953-958, Attwood et al., Polymer Preprints, 20, no. 1, April 1979, pp. 191-194; and Rueda et al., Polymer Communications, 1983, vol. 24, September, pp. 258-260. In recent years, Imperial Chemical Industries, LTD (ICI) has been offering commercially a PAEK called Victrex (a trademark of ICI) PEEK. As PAEK is the acronym of poly(aryl ether ketone), PEEK is the acronym of poly(ether ether ketone) in which the phenylene units in the structure are assumed.
According to Attwood et al., Polymer, 1981, supra, the PAEKs formed by electrophilic and nucleophilic aromatic substitution have a tendency to possess branching, the degree of branching being determined by the process employed. Branching is the essential phenomena being minimized in Dahl, U.S. Pat. No. 4,247,682, Agolino, U.S. Pat. No. 3,668,057, and Angelo et al., U.S. Pat. No. 3,767,620.
Thus PAEKs are well known; they can be made from a variety of starting materials; and they can be made with different melting temperatures and molecular weights. Nominally, PAEKs are crystalline and can be made tough, i.e., exhibit high values (&gt;50 ft-lbs/in.sup.2) in the tensile impact test (ASTM D-1822). They have potential for a wide variety of uses, but because of the significant cost to manufacture them, they are extremely expensive polymers. Their favorable properties classes them with the best of the engineering polymers.
Polymer blends have been widely taught and employed in the art. As broad as this statement may be, the blending of polymers remains an empirical art and the selection of polymers for a blend giving special properties is, in the main, an Edisonian-like choice. Certain attributes of polymer blends are more unique than others. The more unique attributes when found in a blend tend to be unanticipated properties.
(A) According to Zoller and Hoehn, Journal of Polymer Science, Polymer Physics Edition, vol. 20, pp. 1385-1397 (1982)
"Blending of polymers is a useful technique to obtain properties in thermoplastic materials not readily achieved in a single polymer. Virtually all technologically important properties can be improved in this way, some of the more important ones being flow properties, mechanical properties (especially impact strength), thermal stability, and price. PA1 . . . Ultimately, the goal of such modeling and correlation studies should be the prediction of blend properties from the properties of the pure components alone. We are certainly very far from achieving this goal." PA1 (C) "Miscibility in polymer-polymer blends is a subject of widespread theoretical as well as practical interest currently. In the past decade or so the number of blend systems that are known to be miscible has increased considerably. Moreover, a number of systems have been found that exhibit upper or lower critical solution temperatures, i.e., complete miscibility only in limited temperature ranges. Modern thermodynamic theories have had limited success to date in predicting miscibility behavior in detail. These limitations have spawned a degree of pessimism regarding the likelihood that any practical theory can be developed that can accommodate the real complexities that nature has bestowed on polymer-polymer interactions." Kambour, Bendler, Bopp. Macromolecules, 1983, 16, 753. PA1 (D) "The vast majority of polymer pairs form two-phase blends after mixing as can be surmised from the small entropy of mixing for very large molecules. These blends are generally characterized by opacity, distinct thermal transitions, and poor mechanical properties. However, special precautions in the preparation of two-phase blends can yield composites with superior mechanical properties. These materials play a major role in the polymer industry, in several instances commanding a larger market than either of the pure components." Olabisi, Robeson and Shaw, Polymer-Polymer Miscibility, 1979, published by Academic Press, New York, N.Y., p. 7. PA1 (E) "It is well known that, regarding the mixing of thermoplastic polymers, incompatibility is the rule and miscibility and even partial miscibility is the exception. Since most thermoplastic polymers are immiscible in other thermoplastic polymers, the discovery of a homogeneous mixture or partially miscible mixture of two or more thermoplastic polymers is, indeed, inherently unpredictable with any degree of certainty, for example, see P. J. Flory, Principles of Polymer Chemistry, Cornell University Press, 1953, Chapter 13, page 555." Younes, U.S. Pat. No. 4,371,672. PA1 (F) "The study of polymer blends has assumed an ever-increasing importance in recent years and the resulting research effort has led to the discovery of a number of miscible polymer combinations. Complete miscibility is an unusual property in binary polymer mixtures which normally tend to form phase-separated systems. Much of the work has been of a qualitative nature, however, and variables such as molecular weight and conditions of blend preparation have often been overlooked. The criteria for establishing miscibility are also varied and may not always all be applicable to particular systems." Saeki, Cowie and McEwen, Polymer, 1983, vol. 24, January, p. 60. PA1 "Isomorphism in macromolecular systems may be defined as the statistical substitution, within a single crystalline phase, between monomer units differing either in chemical structure or in conformation or in configuration. The distribution of the different monomer units needs not to be totally random. As we shall see, there are examples of isomorphous systems consisting of a mixture of different homopolymer chains. In these cases the randomness is confined to the macromolecules and is not extended to the monomer units by themselves. There are systems containing two (or more) types of monomer units where a unique crystal structure is observed for every composition. In other cases more than one crystalline phase containing both types of units is detected, depending on the composition and/or thermal or mechanical treatments. Following NATTA we shall indicate the phenomenon of the first type as isomorphism in a strict sense and that of the second type as isodimorphism or isopolymorphism. It is apparent that our introductory definition of isomorphism is general in that it applies to both cases; in the general meaning we will also use the equivalent terms isomorphous replacement and cocrystallization. PA1 Bunn and Peiser first recognized macromolecular isomorphism in synthetic materials in the case of the ethylene/vinyl alcohol copolymers and in polyvinylalcohol itself. Successively, they suggested this possibility also for natural rubber. Subsequently, many other examples of macromolecular isomorphism were described. We shall see in the following that they refer mainly to stereoregular vinyl polymers and copolymers, fluorinated polymers and copolymers, copolyamides, and polyesters. In this review we shall refer only to synthetic materials, excluding therefore such important examples of isomorphism as those occurring in polypeptides and polynucleotides." (pp. 549,550) PA1 "The most important conditions to be fulfilled in order to have isomorphism in a macromolecular system are: PA1 "***as would be expected from the greater polarity of the carbonyl group; the high T.sub.m of polymer VIII is due to increased chain rigidity introduced via the biphenylene group. It is surprising that those polymers containing only carbonyl and ether inter-ring linkages (all except VIII and IX in Table 8) should have the same crystal structure, for their chemical repeat units differ substantially, especially in length. However, the unit cell of polymer III has been determined by X-ray diffraction and the fibre repeat distance found to be 10.0 A. This does not correspond to the chemical repeat unit, but to a shorter unit consisting of two phenylene rings joined either by two ether links or one ether and one carbonyl (FIG. 2). All bonds in the linking groups lie in the same plane and the average angle between bonds linking phenylene rings is .about.1240. Thus, in this polymer and all the others in Table 8 containing only ether and carbonyl linkages between the rings these linkages are stereochemically equivalent to such an extent that the polymers have virtually the same crystal structure. Polymer VIII, although well crystalline, does not have the same crystal structure. This is not surprising as the presence of direct inter-ring linkages must alter the chain conformation." PA1 "The similarity of the unit cell and of the chain conformations of these polymers strongly suggest that the crystal structure of Boon et al. for poly(phenylene oxide) is also a good model for the present aryl ether ketone polymers." PA1 "[i]n addition to the general steric requirements reported in the introductory section for macromolecular isomorphism, if chains differ in chemical structure, they must also show some degree of compatibility* to intimate mixing and not too much different crystallization kinetics. The first condition is strictly similar to the one that applies to liquid mixtures. As a well known example, liquids without reciprocal affinity in general cannot form a unique phase. Attempts to obtain mixed crystals from polyethylene and polyvinyl or polyvinylidene fluoride has been unsuccessful hitherto, in spite of the similarity in shape and size of their chains. In view of the above somewhat strict requirements, it is not suprising that relatively few examples of this type of isomorphism have been reported." (emphasis added) FNT *In this instance the authors are using "compatibility" where miscibility is believed to be the intended word. Miscibility means a homogeneous mixture whereas compatibility means useful properties when mixed and molded. PA1 (i) at least one aromatic diacyl halide of the formula: EQU YOC--Ar--COY PA1 where --Ar-- is a divalent aromatic radical, Y is halogen and COY is an aromatically bound acyl halide group, which diacyl halide is polymerizable with at least one aromatic compound of (a)(ii), and PA1 (ii) at least one aromatic compound of the formula: EQU H--Ar'--H PA1 wherein --Ar'-- is a divalent aromatic radical and H is an aromatically bound hydrogen atom, which compound is polymerizable with at least one diacyl halide of (a)(i)
In the field of miscibility or compatibility of polymer blends, the art has found predictability to be unattainable, even though considerable work on the matter has been done. According to authorities:
(B) "It is well known that compatible polymer blends are rare." Wang and Cooper, Journal of Polymer Science, Polymer Physics Edition, vol. 21, p. 11 (1983).
Miscible polymer blends are not common, and those of different PAEs and PAEKs are unique to most uncommon. However rarified the phenomena miscibility may be, even more so is the phenomena of isomorphism. According to Allegra and Bassi, Adv. Polymer Sci., vol. 6, pp. 549-574 (1959) in their article entitled "Isomorphism in Synthetic Macromolecular Systems"
At p. 550, Allegra et al. set forth requirements for isomorphism as follows:
(i) the different types of monomer units must approximately have the same shape, and occupy the same volume, and PA2 (ii) the same chain conformation must be compatible with either of them."
According to Attwood et al., Polymer, 1981 p. 1102, supra PAEKs T.sub.m and T.sub.g increase "as the ratio of carbonyl to ether linkages increase(s):
Accordingly, Dawson and Blundell, Polymer, 1980, vol. 21, 577-578, at 578, assume that the cited PAEKs, because of:
However, Allegra et al, supra, at p. 567, in discussing isomorphism of macromolecules with different chemical constitution find that
This, of course, established the non-congruity of attempting to draw conclusions about mixed polymer isomorphism discussed by Allegra et al (p. 567) and the unit cell and chain conformation similarities noted for some PAEKs homopolymers and copolymers by Dawson and Blundell, supra, and Attwood et al., Polymer Preprints, supra, at page 194.
The complexity of prognosis of miscibility or compatibility, indeed of the kind denoting isomorphism, for any blends of PAEKs is made more so by the issue of branching inherent to varying degrees in PAEKs. Compare the result from blending low density polyethylene with high density polyethylene. There the degree of branching is the only molecular difference and mixtures of them are not isomorphic.
Moreover, prior data noting the very rare case of random copolymer isomorphism as compared with polymer blend isomorphic behavior have noted different melting temperature composition data (Natta et al, Journal of Polymer Science, Part A3, 4263 (1965)). Indeed, Allegra et al., supra, have classed them differently. As with many other properties (e.g. miscibility, transparency, etc.) random copolymers generally exhibit widely different properties than blends of the polymers based on the individual monomer constituents of the copolymer (e.g. comparison of styrene-acrylonitrile copolymer properties with those of polystyrene/polyacrylonitrile blends).